WASHINGTON—A recent NBC News report is reviving controversy over a commonly used recycled rubber product that many officials in the rubber industry say is harmless and highly useful to many, a possible carcinogen to others.

“Not to downplay the seriousness of this issue,” said Michael Blumenthal, founder of consulting firm Marshay Inc. and former Rubber Manufacturers Association vice president. “But now it boils down to this: those who like crumb rubber artificial turf, and those who don't.”

The Oct. 8 NBC story, “How Safe Is the Artificial Turf Your Child Plays On?” told of efforts of Amy Griffin, associate head coach for the women's soccer team at the University of Washington, to compile a list of young soccer players contracting leukemia, lymphoma and other blood cancers after two goalies she knew were diagnosed with non-Hodgkin's lymphoma.

Griffin found 38 U.S. soccer players with blood cancers, including 34 goalkeepers. Besides being soccer players, the one thing they had in common was that they often played on artificial turf made with crumb rubber granules.

“The tiny black rubber crumbs of which the fields are made—chunks of old tires—get everywhere: in players' uniforms, in their hair, in their cleats,” wrote Hannah Rappleye, NBC News reporter.

“But for goalkeepers, whose bodies are in constant contact with the turf, it can be far worse,” Rappleye wrote. “In practices and games, they make hundreds of dives, and each plunge sends a black cloud of tire pellets into the air. The granules get into their cuts and scrapes, and into their mouths.”

The NBC story was a catalyst for follow-up stories in other news outlets and environmental blogs across the U.S.

“While a direct link hasn't been proven, it does raise an alarming question: why would young soccer players, and especially goalies who spend a lot of time on the ground, suddenly be at risk for cancer?” wrote Caroline Cox, research director for the Oakland, Calif.-based Center for Environmental Health, in an Oct. 9 story for the CEH website. Several years ago, the CEH won a settlement with artificial turf manufacturers to stop using lead as a pigment stabilizer.

The story also motivated Rep. Frank Pallone, D-N.J., to write the Agency for Toxic Substances and Disease Registry, calling for an official study of the potential health risks of crumb rubber in artificial athletic turf.

“It is clear that more data is needed to evaluate the risks that exist from exposure to crumb rubber in athletic turf and its effect on human health,” he wrote in his Oct. 10 letter.

The preponderance of evidence

The U.S. Environmental Protection Agency quotes the Synthetic Turf Council as saying that an estimated 4,500 U.S. athletic fields, running tracks and playgrounds have installed crumb rubber synthetic turf.

Many scientific, industry, state government and environmental groups have performed studies concerning the possible health effects of crumb rubber artificial turf. Most studies to date have shown exposures too low to harm humans, but worry persists.

One of the latest negative studies was published in January 2013 in the scientific journal Chemosphere.

“Studies of the vapor phase above the samples confirm the volatilization of many of these organic compounds,” the abstract to the study said. “Uses of recycled rubber tires, especially those targeting play areas and other facilities for children, should be a matter of regulatory concern.”

On the other side, both the RMA and the STC have performed summaries of existing health and environmental studies of crumb rubber athletic turf. Both organizations reached the same conclusion.

“There is a considerable body of research on artificial turf, and it reveals no cumulative risk,” said Dan Zielinski, RMA vice president of public affairs.

After the NBC News story aired, the STC issued a statement.

“During the past two decades, there have been more than 60 technical studies and reports that review the health effects of crumb rubber,” the STC said. “The preponderance of evidence show no negative health effects associated with crumb rubber in synthetic turf.”

The tire recycling industry hailed the December 2009 issuance of an EPA study that found very low levels of toxic substances at four athletic turf sites in North Carolina, Maryland, Georgia and Ohio.

According to a page on the EPA website, the study found that airborne levels of particulate matter, metals and volatile organic compounds were no higher on the athletic fields than they were in nearby areas.

All air concentrations of lead, zinc and particulate matter were below levels of concern, and no tire-related fibers were found at all, the agency said.

However, the EPA also warned against making general conclusions about the study results.

“Given the very limited nature of the study ... and the wide diversity of the crumb material, it is not possible to extend the results beyond the four study sites or to reach any comprehensive conclusions without the consideration of additional data,” the agency said.

In any case, the EPA has no current plans to conduct another study, although it continues to monitor the issue closely, according to an agency statement.

“The agency believes that more testing needs to be done, but currently the decision to use tire crumb remains a state and local one,” it said.

What happens next?

The benefits of crumb rubber synthetic turf are apparent even to some of its detractors. It provides a soft, springy surface that reduces the possibility of injury; it requires no water, fertilizer or pesticides, thus saving both money and natural resources; and it keeps scrap tires out of landfills and stockpiles.

Nevertheless, because of the uncertainty surrounding the issue of toxics, some municipal entities have stopped using crumb rubber in favor of alternative substances. The New York City Parks Department installed its last crumb rubber turf in 2008, the Los Angeles Unified School District in 2009.

Of the substances in recycled tires, the CEH is most concerned about zinc, benzothiozole and carbon black, according to Cox. Carbon black is of particular concern, she said, because it comprises 20 to 40 percent of the weight of a tire.

But instead of seeking either legal action or further studies, the CEH is seeking a more community-based response to crumb rubber, encouraging schools and parks to use alternative infills such as cork and coconut husks, she said.

“Using artificial turf just postpones the date a scrap tire goes to the landfill, rather than keeping it out altogether,” Cox said. “Rather than argue about whether crumb rubber is toxic, we think that alternative products are a safer way to go. We could spend a lot of money on studies that could take 20 years, or we could use alternatives.”

To Blumenthal, the record is clear that crumb rubber artificial turf presents no danger to anybody.

There is a lot of anger over these incidences of blood cancers, and when there are a lot of cases that have common threads—i.e. soccer players playing on artificial turf—suspicions tend to run toward those threads, according to Blumenthal.

“But if you look around the world, where they have been using crumb rubber on soccer fields for many more years than the U.S. has, you will find no elevated instances of cancer,” he said.

For the crumb rubber industry, the NBC News report was done more for effect than for in-depth reporting, according to Blumenthal.

“But because of this story, there are those who will always have that question in the back of their minds,” he said. “It's a news story, and we have to deal with it.”